1. Field of the Invention
The present invention relates to high-energy radiation detectors and in particular to a portable radiation detector of the type having a housing containing a radiation transducer.
2. Description Of the Prior Art
German OS 25 19 640 discloses a dental x-ray diagnostics installation that has an automatic exposure unit for controlling the radiation generator in order to obtain an optimum exposure of an x-ray film. For producing an x-ray exposure, a film holder is arranged in the mouth of a patient, this film holder carrying a dental x-ray film in a pocket. A detector/transmitter circuit that wirelessly emits an electrical signal corresponding to the film blackening is adjacent to the pocket. This signal is received by an antenna and is supplied to the automatic exposure unit which controls the radiation source. The automatic exposure unit effects a turn-off of the radiation when the dose corresponding to the desired film blackening has been reached.
The detector/transmitter circuit is fashioned as an integrated component and includes a phosphor layer behind which a light-sensitive detector is arranged. The phosphor layer is excited to luminesce dependent on the incident radiation dose. The light emitted by the phosphor layer is converted into an electrical output signal by the detector, this electrical output signal thus being a measure for the radiation intensity. The output signal is amplified in an amplifier and integrated in an integrator. The integrator is followed by a trigger circuit whose threshold can be set with a reference value generator to correspond to the sensitivity of the x-ray film. The trigger circuit controls the activation and deactivation of the transmitter. A voltage supply is provided in the detector/transmitter circuit that contains a switch with which the operating voltage can be connected to the components. It is known that a detector that is directly sensitive for x-rays can also be employed.
European Application 0 544 974 discloses a radiation detector constructed with a CCD converter whose individual detector cells generate output signals dependent on incident radiation. These output signals can be supplied to a computational unit that, for example, produces a fluoroscopic image of a subject on a monitor. The CCD converter is connected via an electrical line and/or via fiber optics to an isolating unit in which the signals are electrically decoupled and are supplied via a cable to a computer serving as computational unit. The employment of electrical lines and/or fiber optics is simple and is thus less cost-intensive; moreover, external disturbances are effectively shielded or are least reduced to a minimum. The infeed and outfeed of the signals as well as the voltage supply of the CCD converter ensues via the isolating unit and via the cable or the fiber optics.
German OS 42 35 527 discloses a signal acquisition device containing a CCD which is connected to a control unit arranged outside the acquisition device. The signals of the CCD are transmitted via a cable to detector circuitry arranged outside the control unit.
Computed tomography systems are disclosed in U.S. Pat. No. 4,912,735, U.S. Pat. No. 5,140,696 and U.S. Pat. No. 5,134,639. Such computed tomography systems have a radiation detector with individual detector cells connected to one another that convert incident radiation into signals. The signals are inductively transmitted according to U.S. Pat. No. 4,912,735, capacitively transmitted according to U.S. Pat. No. 5,140,696 and electro-optically transmitted according to U.S. Pat. No. 5,134,639.